New Tests of General Relativity: Next Generation Lunar Laser Ranging

Forty years ago, three retroreflector arrays were deployed on the moon, the first during Apollo 11 by Neal Armstrong This is the only Apollo era experiment still operating. Our continuing ranging program has produced many of the best tests of General Relativity i.e., the change in G with time, the inertial properties of gravitational energy and the strong equivalence principle. The lunar laser ranging observatories have improved their ranging accuracy by two orders of magnitude, so now the combination of the lunar librations and the design of the arrays limit the accuracy. The next generation of retroreflectors, the “Lunar Laser Ranging Retroreflectors for the 21st Century” or LLRRA-21, are being developed at the University of Maryland in collaboration with INFN-LNF in Italy. The LLRRA-21 program will be described: the science objectives, both for General Relativity and for Lunar Physics, the technical objectives, the design parameters, the thermal simulation, the thermal vacuum testing, the various deployment possibilities and the flight opportunities.